If you are using Microsoft Outlook 2011 for email and you connect to an exchange server, you might want to hold off on upgrading to El Capitan. The two don't get along and you get a spinning beachball when you launch it and connect to an exchange server. There are some suggested fixes; none worked for me. Had I known, I would have waited. Microsoft is aware of the problem; I hope they release a fix very soon._________________Mini 1 (2012): 2.3 ghz Core i7; 16gb RAM, Corsair 240gb SSD, 500gb Seagate XT
Mini 2 (2009): 2.26 ghz Core 2 duo, 8gb RAM, 500gb SSD running Ubuntu
Also a 13" MacBook Air, 21.5" i5 iMac & 11.6" Acer 1810TZ running Ubuntu, openSUSE & Crunchbang

Diskutil in El Capitan has no longer the option to create a RAID. Many recommend either using a thrid party piece of software or else using the terminal command windows. No longer confident enoguh to do the latter and the third party option is expensive.

Easiest way is to make sure that you have a Time Machine backup of a previous version and boot off that and use then disk util in that. This worked on my 2012 mac mini with Yosemite.